The present invention relates to control panels for controlling apparatus or appliances of various types, and is more particularly concerned with control panels that are touch sensitive. The invention is more specifically directed to touch-sensitive control panels that are made substantially rigid and avoid mechanical switch elements.
The invention is also concerned with a control panel that is provided with a generally flat rigid or semi-rigid front panel or plate, and which has capacitive touch sensor pads behind the front panel, and which can be hermetically sealed for use in harsh environments.
Touch sensors are an attractive choice in many environments because they require no moving parts, and the surface presented to the user can be a plain, smooth surface which can be sealed to prevent moisture, dust, and contaminates from entering and compromising the control panel, and which can be easily cleaned. Also the touch sensors may be made transparent or translucent, at least in part, which permits them to be back-lit, e.g., with LEDs, to assist or guide the user or operator when employing the touch panel to set or operate the associated equipment.
One example of an application for a control panel where a capacitive touch screen can provide an advantage is in a controller for pool-and-spa equipment such as a water heater or heater and chiller, where the controls are or may be exposed to moisture and caustic chemicals. These control panels are typically mounted on the shell or housing of a pool water heater or pool-and-spa water heater, which may also include pump and filtration equipment. This equipment may be in the form of a heat pump which can be configured for cooling as well as heating the water for the pool and/or spa. At a minimum, this would require the controls to switch between modes for heating and cooling, and to allow the operator to adjust the heating and possibly cooling setpoints for the pool and for the spa or hot-tub.
The control panel also includes a display, visible through a transparent window zone of the front panel, that can show the water temperature, the programmed temperature setpoint(s), and indications of the mode and of which features are active and can be selected and changed.
The capacitive touch-screen control panel can be employed in many other applications as well, for example, in adjusting the height of a work space desk or work surface in an emergency work station.
Favorably the panel front plate is a simple rigid, impervious plate of a durable material, such as an acrylic, a polycarbonate, or glass, for example, which is robust and can be suitably transparent, and which has a sufficiently high dielectric constant so that the capacitive electrode pads will pick up the presence of an operator's finger when placed on the front surface of the panel front plate.
Previous control panels typically employ a touch screen keypad with one or more rows of membrane switches for select, mode, temperature increment up, and temperature increment down functions. The membrane switch keypad is adhered to the rigid plastic front plate, and an associated printed circuit board is mounted inside the cabinet behind the board. The printed circuit board is then connected by a cable to the pool heater or pool heat pump equipment. In these arrangements LED alpha-numeric display modules are mounted on the printed circuit board and are visible through a window on the front panel or plate. These alpha-numeric display modules have to be mounted on the front or facing side of the board and electrically connected with conductive traces on that side of the board. Consequently, the board has to be spaced or offset behind the front plate to provide clearance for the display modules and also for a number of LED indicators that are also visible through the window of the front plate to indicate modes and settings.
The membrane switches have a limited life span, and can crack and leak, leading to switch failures.